WHY IT'S A BREAKTHROUGH: This SPF spray sticks to soaking-wet skin so you don't have to dry off to stay protected. Silicones and a wax derived from the oil in lotus flowers help repel moisture. It's similar to the mechanism that causes water to bead up and roll off the flower's leaves during heavy rain. Still, this stuff doesn't make you impervious to the elements. You'll need to reapply every two hours, no matter what.